package com.leo.persistence.sqlSession;

import com.leo.persistence.config.SqlCommandType;
import com.leo.persistence.pojo.Configuration;
import com.leo.persistence.pojo.MappedStatement;

import java.lang.reflect.*;
import java.sql.SQLException;
import java.util.List;

/**
 * 线程不安全，一个SqlSession实例持有一个Connection，外部ThreadLocal解决
 */
public class DefaultSqlSession implements SqlSession {

    // 线程不安全
    private SimpleExecutor executor = new SimpleExecutor();
    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> E selectOne(String statementId, Object... params) throws Exception {
        List<E> objects = selectList(statementId, params);
        if (objects.size() == 1) {
            return objects.get(0);
        } else {
            //throw new RuntimeException("查询结果为空或者返回结果过多");
            return null;
        }
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);

        List<E> objectList = executor.executeQuery(configuration, mappedStatement, params);

        return objectList;
    }

    @Override
    public int insert(String statementId, Object... params) throws Exception {
        return update(statementId, params);
    }

    @Override
    public int update(String statementId, Object... params) throws Exception {
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return executor.executeUpdate(configuration, mappedStatement, params);
    }

    @Override
    public int delete(String statementId, Object... params) throws Exception {
        return update(statementId, params);
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        Object proxyInstance = Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();

                String statementId = className + "." + methodName;
                SqlCommandType sqlCommandType = configuration.getMappedStatementMap().get(statementId).getSqlCommandType();

                switch (sqlCommandType){
                    case SELECT:
                        // 准备参数2：params:args
                        // 获取被调用方法的返回值类型
                        Type genericReturnType = method.getGenericReturnType();
                        // 判断是否进行了 泛型类型参数化
                        if (genericReturnType instanceof ParameterizedType) {
                            List<Object> objects = selectList(statementId, args);
                            return objects;
                        }
                        return selectOne(statementId, args);

                    case INSERT:
                        return insert(statementId, args);
                    case UPDATE:
                        return update(statementId, args);
                    case DELETE:
                        return delete(statementId, args);
                    default:
                        return new RuntimeException("暂不支持");
                }
            }
        });
        return (T) proxyInstance;
    }
}
